Continuous casters in the metals industry typically pour liquid, molten metal into a mold at the top of the caster (through an SEN tube). A granular mold powder is layered atop the open caster top in order to (i) prevent oxidation (scale) at the top molten metal surface and when melted (ii) provide a side wall lubricant for the cast as it proceeds down through the caster.
The mold powder is consumed as the cast proceeds, but at different rates depending on the liquid metal flow patterns and sidewall drag. Our goal is to be able to measure the mold powder layer thickness and use the measurement to determine areas that need additional mold powder. Absent such automated measurement and application feed rate control, it is common for a human to make a thickness estimation after which the human laborer “rakes” on the appropriate powder layer at the appropriate locations as the powder is consumed. This laborer works in a location, which is both hot and dangerous. Remote control of a variable rate granular powder feeder can put the human in a more protected place, but the accurate determination of the granular powder depth across the mold top is still required.
Mold powder is consumed at a variable rate depending on the dynamics of the cast. It has been shown that simply feeding mold powder at a consistent rate will not maintain the desired powder thickness across the entire top area. Too much powder in a given area will modify the powder chemistry/sintering (creating what the industry calls “roping”); while too little powder thickness in a given area may permit the molten metal to be exposed resulting in slag production, which become defects within the cast. Too little mold powder also results in a shortage of sidewall lubricant and even the possibility of producing a catastrophic “caster breakout”.
We have determined that the distance measurement obtained from a TOF (Time of Flight) laser sensor is accurate and robust when utilized to measure the top surface powder height at a specific point in the top of the continuous caster. Additionally, the TOF sensor robustly and accurately measures the height of the underlying molten flux or molten steel level absent the powder. This disclosure presents a method of utilizing either a TOF laser sensor or other small diameter beam laser distance sensor in conjunction with a novel high-pressure gas puff to determine both the granular powder depth and height of the underlying liquid layer.
We desire to provide a constant powder layer thickness using an actual granulated layer thickness measurement system capable of accurate measurement in the hostile environment atop a caster; thereby, permitting feedback control of a granular mold powder feed and distribution mechanism.